654 
NATURE 
[ April 28, 1870 
A Word in Defence of Physicists. 
Two passages in NATURE of April 14th show that the sup- 
posed opposition between geologists and physicists is not forgotten. 
This feud can only impede the advancement of truth. 
Prof. Duncan, inhis instructive paperon Dr. Carpenter’s Report, 
writes thus ;—‘‘ Physicists have propounded theories which have 
been accepted by some geologists, but they are looked upon as 
doubtful hypotheses by others. Palaeontologists and such theories 
have been constantly at issue. The theories involving pressure, 
and the hardness of deep-sea deposits, will suffer from the re- 
searches ; but many difficulties in the way of palzontologists will 
be removed.” 
I cannot think that either of the ‘‘theories,” to which allusion 
appears to be made, can ever have been accepted by any one who 
understood the nature of fluid pressure. The tissues of a living 
being inhabiting the depths must necessarily be permeated by 
liquids at the same pressure as that of the water without. Hence 
no crushing effect can be produced. So, too, the particles of 
mud or sand at the bottom of the ocean are buoyed up by water 
at the same pressure as that by which they are forced down, and 
they sink only by the difference of weight between themselves 
and the dense water ; so that the ooze at a profound depth ought 
actually to lie lighter than beneath shallower water. These con- 
siderations have always occurred to me when reading about the 
misconceptions to which Prof. Duncan alludes, But what I wish 
to point out is, that it is not the deductions of physicists which are 
overthrown, but the fancies of those who are not physicists, 
which were always opposed to physical principles. 
Mr. Wilson’s letter about ‘‘ geological time” may possibly 
elicit a reply from Professor Pritchard. But why is Sir W. 
Thomson’s name introduced into the heading? And does Mr. 
Wilson intend to tell us that Mr. Darwin considers natural selec- 
tion incompetent to produce the human eye? For unless Mr. 
Darwin admits direct destgz in the arrangement of the human 
eye, it does not appear how Mr. Pritchard’s /apsus in seem- 
ing to include man among the Articulata, can yitiate his argu- 
ment as against Darwin. O, FISHER 
Heat Units 
In No, 24 of NAtTuRE (April 14) Mr. Thomas Muir calls 
atention to the inconvenience arising from the want of some 
uniform and generally recognised mode of expressing qualities 
of heat. As there can be no question that the inconyenience 
isa real one, I venture to suggest as one remedy for it, the 
employment of the following terms, namely— 
grain-degree, 
pound-degree, 
gramme-degree 
kilogramme-degree, 
to denote respectively the quantities of heat required to raise the 
temperature of one grain, pound, gramme, or kilogramme of 
water from 0° to 1° Centigrade. These expressions are used in 
the article Heat, in Watts’s ‘‘ Dictionary of Chemistry”; and 
having been for several years in the habit of using them in 
my lectures, Iam able to say from experience that the employ- 
ment of them greatly facilitates statements relating to quantities 
of heat. 
It appears to me to be in favour of these terms, as compared 
with Mr. Muir’s “therm,” ‘‘kilotherm,” &c., that they enable 
us to do without the formation of any new word, that they are 
self-interpreting, and that by means of them quantities of heat 
can be expressed with reference to the British or to the metrical 
standards of mass, with equal facility. 
University College, London, April 25. G. C, FOSTER 
The Sun’s Chromosphere 
Is there any way, by means of an ordinary telescope with 
coloured glasses, of seeing the red prominences on the sun’s edge 
—that is, without a spectroscope? If so, what coloured glasses 
ought to be used? In one of the former numbers of NA1URE, 
an observer saw, with only a telescope, what he believed to be 
these prominences ; the sun was near the horizon, a series of 
rose-coloured undulations became visible, unconnected, as sup- 
posed, with atmospheric disturbance, and which it was suggested 
might be due to the red flames of the chromosphere. 
A. 
Lefthandedness 
In a letter on this subject by J. S., in this week’s number of - 
Narurg, the hypothesis is mentioned that left-handed persons 
may owe their peculiarity to a transposition of the viscera, or at 
least of the great arteries of the upper limbs. This supposition, 
which has been more than once advanced, is certainly not true. 
Several cases of transposition of viscera are on record in which 
the persons affected were right-handed. One was recorded by 
M. Gery (quoted in Cruveillier’s Azatomie, tome I, p. 65, 
note), another by M. Gachet (Gazette des Hopitaux, Aug. 31, 
1861), and a third in the Pathological Transactions, vol. xix., 
P- 447- 
Your correspondent’s opinion seems probable that righthanded- 
ness is the result partly of hereditary, partly of individual educa- 
tion, and is intimately associated with the more complex func- 
tions of the hand. PS. 
April 18, 1870 
THE ABRADING AND TRANSPORTING 
POWER OF WATER 
IIl.—FRICTION OF WATER 
@y a former occasion the abrading and _ transporting 
power of water (which is supposed to increase as 
the velocity increases, but to decrease as the depth in- 
creases) was considered from a mechanical point of view, 
and arguments were brought forward to show that water 
rolls rather than slides. The question then arises— 
1. How does flowing water obtain this rolling motion ? 
The reply to this is, By /rzctzon. 
Take, for example, the rifling of a gun; we all know 
that it is owing to the spiral grooves or prominences in the 
chamber that the shot gets its spinning motion; but 
supposing the shot be a sphere, and fired from a smooth 
bore, it has not this rotatory motion at right angles 
to the line of flight, and no great dependence can be 
placed on its accuracy, but it may rise or fall, pass 
to the right or left, all depending on which side of the 
gun’s mouth the shot touched when passing out, for so 
will it revolve. Should it ricochet, it will, when nearly 
spent, be observed to roll over the ground, and this is all 
caused by the friction offered by the resistance of the 
ground with which it came in contact. And what reason 
can there be assigned against water adopting this most 
simple of all laws for bodies in motion; and is it not 
owing to this that water in a cistern takes a circular 
motion when escaping through an orifice in its bottom, 
or presents a cork-screw appearance when poured out of 
a small vessel? Again, on the large scale, with rapid 
currents such as in the Pentland Frith, what but this cir- 
cular motion of the stream can cause that boiling ap- 
appearance given to the water, which everyone must have 
observed who has navigated waters where there is a strong 
tideway? And cannot this explain why there should be 
an enormous breaking sea at the point where the heavy 
swell of the Atlantic meets the ebb tide; and does not 
this rolling motion given to the tide, acting in an opposite 
direction, check the oscillations of the Atlantic swell, 
causing those huge breakers so well known to the Orca- 
dian boatmen ? 
Supposing every particle of water to be a sphere in 
itself that can roll independently, and that a number of 
them being collected together form a larger sphere, which 
also rolls, and so on, then the diameter of the spheres 
increases with the depth, be it ever so great. Conse- 
quently, the facility for rolling will also increase, so that 
the deeper and broader a stream is—that is, the farther 
the centre of a stream is from the retarding medium (the 
bed and banks ofa river)—the less 1s this rotatory motion 
obstructed ; and does not this explain how the velocity 
increases with the hydraulic mean depth? The air also 
has a retarding effect even in a perfect calm; for where 
the Mississippi was very deep, it has been observed that 
